Framing Method and Apparatus in Passive Optical Network and System

ABSTRACT

A framing method and apparatus in a passive optical network (PON) and a system, where the method includes generating a first transmission convergence (TC) frame and a second TC frame separately, wherein a sum of frame lengths of the first and the second TC frame is 125 microseconds (μs), performing bit mapping on the second TC frame to generate a third TC frame, where the bit mapping refers to identifying each bit of the second TC frame using N bits, and sending the first and the second TC frame to an optical network unit (ONU). A line rate corresponding to the second TC frame is lower than 2.488 giga bits per second (Gbps) such that a rate of a receiver on a receiving side is decreased and a bandwidth of the receiver is narrowed, thereby decreasing an optical link loss and increasing an optical power budget.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2015/079415 filed on May 20, 2015, which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the communications field, and inparticular, to a framing method and apparatus in a passive opticalnetwork (PON), a deframing method and apparatus in a PON, and a system.

BACKGROUND

With the rapid development of optical communications technologies, a PONsystem is increasingly widely applied in optical communicationstechnologies. A PON architecture is shown in FIG. 1, and thearchitecture is used as an example for description below. A PON consistsof an optical line terminal (OLT) 110 on an office side, an opticalnetwork unit (ONU) 120 (or an optical network terminal (ONT)) on a userside, and an optical distribution network (ODN) 130. A tree topologystructure is generally used in the PON.

The OLT 110 provides a network side interface to the PON system toconnect one or more ODNs 130. The ONU 120 provides a user side interfaceto the PON system to connect the ODN 130. If the ONU 120 directlyprovides a function of a user port, for example, an Ethernet user portused by a personal computer (PC) to access the Internet, the ONU 120 isreferred to as the ONT 120. Unless otherwise indicated, the ONU 120mentioned below generally refers to the ONU and the ONT. The ODN 130 isa network consisting of an optical fiber and a passive optical splitterconfigured to connect the OLT 110 and the ONU 120 and further configuredto perform distribution or multiplexing on a data signal between the OLT110 and the ONU 120.

In the PON system, a direction from the OLT 110 to the ONU 120 isreferred to as a downstream direction. In contrast, a direction from theONU 120 to the OLT 110 is referred to as an upstream direction. In agigabit-capable PON (GPON), based on a specification in the currentInternational telecommunication Union (ITU) G.984 series standards, adownstream transmission rate is generally 2.488 gigabits per second(Gbps) (i.e. 2488 megabits per second (Mbps)), and only one downstreamtransmission rate exists during running of the entire system.

Generally, in design of an optical network, to ensure that requiredperformance levels are reached in various optical transmission sections,a budget of a total optical power loss needs to be planned, where thebudget is referred to as an optical power budget. Losses allowable inthe optical power budget are defined as optical losses S/R and R/S (Sdenotes a reference point of optical signal sending, and R denotes areference point of optical signal receiving) between reference points,which are expressed in decibels (dB). The loss includes a loss caused byan optical fiber and a loss caused by a passive optical element. In anexisting ODN network, an optical power budget may become insufficientbecause an optical link loss increases. Therefore, how to increase anoptical power budget of a PON system is a problem that urgently needs tobe resolved.

SUMMARY

In view of this, embodiments of the present disclosure provide a framingmethod and apparatus in a PON system and a deframing method andapparatus in a PON system, which can increase an optical power budget ofthe PON system.

According to a first aspect, a framing method in a PON is provided,including generating a first transmission convergence (TC) frame and asecond TC frame separately, where a downstream rate of the first TCframe is 2.488 Gbps or 10 Gbps, a downstream rate of the second TC frameis 1/N of the downstream rate of the first TC frame, and a sum of framelengths of the first TC frame and the second TC frame is 125microseconds (μs), where N is an integer greater than 1, performing bitmapping on the second TC frame to generate a third TC frame, where thebit mapping refers to identifying each bit of the second TC frame usingN bits, and sending the first TC frame and the third TC frame to an ONU.

With reference to the first aspect, in a first possible implementationmanner of the first aspect, the method further includes performing firstcoding on the second TC frame, where the first coding is one ofReed-Solomon code RS (255,239) coding or RS (248,216) coding,low-density parity-check code LDPC coding, or cascade forward errorcorrection (FEC) coding.

With reference to the first aspect or the first possible implementationmanner of the first aspect, in a second possible implementation mannerof the first aspect, the method further includes performing scramblingon the second TC frame.

With reference to the first aspect or the first possible implementationmanner of the first aspect, in a third possible implementation manner ofthe first aspect, the method further includes inserting a pseudo GPONencapsulation method (GEM) frame header into the third TC frame. Bymeans of this implementation manner, an original ONU (the original ONUrefers to an ONU whose receive rate is 2.488 Gbps in a GPON system, oran ONU whose receive rate is 10 Gbps in a 10-GPON (XG-PON)) may notgenerate a GEM frame loss alarm when receiving the third TC frame.

With reference to the third possible implementation manner of the firstaspect, in a fourth possible implementation manner of the first aspect,inserting a pseudo GEM frame header into the third TC frame furtherincludes inserting a placeholder into the third TC frame, performingscrambling on the third TC frame into which the placeholder is inserted,and filling the placeholder using the pseudo GEM frame header.

With reference to the fourth possible implementation manner of the firstaspect, in a fifth possible implementation manner of the first aspect,the method further includes performing second coding on the first TCframe and the third TC frame into which the pseudo GEM frame header isinserted, where the second coding is one of RS (255,239) coding or RS(248,216) coding, LDPC coding, or cascade FEC coding. By means of thisimplementation manner, the original ONU may not generate an FEC alarmwhen receiving the third TC frame.

With reference to the fifth possible implementation manner of the firstaspect, in a sixth possible implementation manner of the first aspect,third scrambling is performed on the first TC frame and the third TCframe that have undergone the second coding.

With reference to the first aspect or any possible implementation mannerof the first aspect, in a seventh possible implementation manner of thefirst aspect, a physical control block downstream (PCBd) field of thesecond TC frame includes a field used to indicate the frame length ofthe second TC frame.

With reference to the first aspect or any possible implementation mannerof the first aspect, in an eighth possible implementation manner of thefirst aspect, the frame length of the first TC frame is an integermultiple of 239 bytes. By means of this implementation manner, in theGPON system, if the frame length of the first TC frame is an integermultiple of 239 bytes, an FEC coding procedure of the first TC frame maybe simplified such that a solution for processing FEC decoding by theONU whose receive rate is 2.488 Gbps is the same as a solution in otherapproaches.

With reference to the first aspect or any of the first to seventhpossible implementation manners of the first aspect, in a ninth possibleimplementation manner of the first aspect, the frame length of the firstTC frame is an integer multiple of 248 bytes. By means of thisimplementation manner, in the XG-PON system, if the frame length of thefirst TC frame is an integer multiple of 248 bytes, an FEC codingprocedure of the first TC frame may be simplified such that a solutionfor processing FEC decoding by the ONU whose receive rate is 10 Gbps isthe same as a solution in the other approaches.

According to a second aspect, a deframing method in a PON is provided,where the method includes receiving a downstream data stream, where thedownstream data stream includes a first TC frame and a second TC frame,where a downstream rate of the first TC frame is 2.488 Gbps or 10 Gbps,a downstream rate of the second TC frame is 1/N of the downstream rateof the first TC frame, and a sum of frame lengths of the first TC frameand the second TC frame is 125 μs, where N is an integer greater than 1,performing synchronization with the first TC frame, and parsing thefirst TC frame.

With reference to the second aspect, in a first possible implementationmanner of the second aspect, the method further includes performingdescrambling on the first TC frame.

With reference to the second aspect or the first possible implementationmanner of the second aspect, in a second possible implementation mannerof the second aspect, the method further includes discarding the secondTC frame.

With reference to the second aspect or any possible implementationmanner of the second aspect, in a third possible implementation mannerof the second aspect, the method further includes decoding the first TCframe.

With reference to the second aspect or any possible implementationmanner of the second aspect, in a fourth possible implementation mannerof the second aspect, discarding the second TC frame includes discardingthe second TC frame according to a port identifier (Port-ID) field of apseudo GEM frame.

With reference to the fourth possible implementation manner of thesecond aspect, in a fifth possible implementation manner of the secondaspect, discarding the second TC frame according to a Port-ID field of apseudo GEM frame further includes discarding the pseudo GEM framecarrying the Port-ID and the second TC frame that is after the pseudoGEM frame when the Port-ID is different from a Port-ID recorded by anONU.

According to a third aspect, a deframing method in a PON is provided,where the method includes receiving a downstream data stream, where thedownstream data stream includes a first TC frame and a second TC frame,where a downstream rate of the first TC frame is 2.488 Gbps or 10 Gbps,a downstream rate of the second TC frame is 1/N of the downstream rateof the first TC frame, and a sum of frame lengths of the first TC frameand the second TC frame is 125 μs, where N is an integer greater than 1,obtaining the second TC frame, performing bit mapping restoration on thesecond TC frame to generate a third TC frame, where the bit mappingrestoration refers to restoration of every N bits in the second TC frameto one bit, and parsing the third TC frame.

With reference to the third aspect, in a first possible implementationmanner of the third aspect, the method further includes performingdescrambling on the second TC frame.

With reference to the third aspect or the first possible implementationmanner of the third aspect, in a second possible implementation manner,the method further includes decoding the second TC frame.

With reference to the third aspect or any possible implementation mannerof the third aspect, in a third possible implementation manner,obtaining the second TC frame includes removing, according to framelength information of the second TC frame that is indicated by a lengthof an asynchronous transfer mode (ATM) block (Alen) field in a PCBdfield of the second TC frame, a pseudo GEM frame from the receivedsecond TC frame, to obtain the second TC frame.

According to a fourth aspect, a framing apparatus is provided, includinga generation module configured to generate a first gigabit-capable PONTC frame and a second TC frame separately, where a downstream rate ofthe first TC frame is 2.488 Gbps or 10 Gbps, a downstream rate of thesecond TC frame is 1/N of the downstream rate of the first TC frame, anda sum of frame lengths of the first TC frame and the second TC frame is125 μs, where N is an integer greater than 1, a mapping moduleconfigured to perform bit mapping on the second TC frame to generate athird TC frame, where the bit mapping refers to identifying each bit ofthe second TC frame using N bits, and a transmission module configuredto send the first TC frame and the third TC frame to an ONU.

With reference to the fourth aspect, in a first possible implementationmanner of the fourth aspect, the apparatus further includes a codingmodule configured to perform coding on the second TC frame, where thefirst coding is one of RS (255,239) coding or RS (248,216) coding, orLDPC coding, or cascade FEC coding.

With reference to the fourth aspect or the first possible implementationmanner of the fourth aspect, in a second possible implementation mannerof the fourth aspect, the apparatus further includes a scramblingmodule, where the scrambling module is configured to perform scramblingon the second TC frame.

With reference to the fourth aspect or any possible implementationmanner of the fourth aspect, in a third possible implementation mannerof the fourth aspect, the apparatus further includes a processing moduleconfigured to insert a pseudo GEM frame header into the third TC frame.

With reference to the fourth possible implementation manner of thefourth aspect, in a fifth possible implementation manner of the fourthaspect, the processing module is further configured to insert aplaceholder into the third TC frame, perform scrambling on the third TCframe into which the placeholder is inserted, and fill the placeholderusing the pseudo GEM frame header.

With reference to the fifth possible implementation manner of the fourthaspect, in a sixth possible implementation manner of the fourth aspect,the coding module is further configured to perform second coding on thefirst TC frame and the third TC frame into which the pseudo GEM frameheader is inserted, where the second coding is one of RS (255,239)coding or RS (248,216) coding, LDPC coding, or cascade FEC coding.

With reference to the sixth possible implementation manner of the fourthaspect, in a seventh possible implementation manner of the fourthaspect, the scrambling module is further configured to performscrambling on the first TC frame and the third TC frame that haveundergone the second coding.

With reference to the fourth aspect or any possible implementationmanner of the fourth aspect, in an eighth possible implementation mannerof the fourth aspect, a physical control block (PCB) field of the secondTC frame includes a field used to indicate the frame length of thesecond TC frame.

With reference to the fourth aspect or any possible implementationmanner of the fourth aspect, in a ninth possible implementation mannerof the fourth aspect, the frame length of the first TC frame is aninteger multiple of 239 bytes.

With reference to the fourth aspect or any one of the first to eighthpossible implementation manners of the fourth aspect, in a tenthpossible implementation manner of the fourth aspect, the frame length ofthe first TC frame is an integer multiple of 248 bytes.

According to a fifth aspect, a deframing apparatus is provided, wherethe apparatus includes a receiving module configured to receive adownstream data stream, where the downstream data stream includes afirst TC frame and a second TC frame, a downstream rate of the first TCframe is 2.488 Gbps or 10 Gbps, a downstream rate of the second TC frameis 1/N of the downstream rate of the first TC frame, and a sum of framelengths of the first TC frame and the second TC frame is 125 μs, where Nis an integer greater than 1, a synchronization module configured toperform synchronization with the first TC frame, and a parsing moduleconfigured to parse the first TC frame.

With reference to the fifth aspect, in a first possible implementationmanner of the fifth aspect, the apparatus further includes adescrambling module configured to perform descrambling on the first TCframe.

With reference to the fifth aspect or the first possible implementationmanner of the fifth aspect, in a second possible implementation mannerof the fifth aspect, the apparatus further includes a decoding moduleconfigured to decode the first TC frame.

With reference to the fifth aspect or any possible implementation mannerof the fifth aspect, in a third possible implementation manner of thefifth aspect, the apparatus further includes a discarding moduleconfigured to discard the second TC frame.

With reference to the third possible implementation manner of the fifthaspect, in a fourth possible implementation manner, the discardingmodule is further configured to discard the second TC according to aPort-ID field of a pseudo GEM frame.

With reference to the fourth possible implementation manner of the fifthaspect, in a fifth possible implementation manner, the discarding moduleis further configured to discard the second TC according to the Port-IDfield of the pseudo GEM frame, where the discarding the second TCfurther includes discarding the pseudo GEM frame carrying the Port-IDand the second TC frame that is after the pseudo GEM frame when that thePort-ID is different from a Port-ID locally recorded by an ONU.

According to a sixth aspect, a deframing apparatus is provided,including a receiving module configured to receive a downstream datastream, where the downstream data stream includes a first TC frame and asecond TC frame, where a downstream rate of the first TC frame is 2.488Gbps or 10 Gbps, a downstream rate of the second TC frame is 1/N of thedownstream rate of the first TC frame, and a sum of frame lengths of thefirst TC frame and the second TC frame is 125 μs, where N is an integergreater than 1, an obtaining module configured to obtain the second TCframe, a restoration module configured to perform bit mappingrestoration on the second TC frame to generate a third TC frame, wherethe bit mapping restoration refers to restoration of every N bits in thesecond TC frame to one bit, and a parsing module configured to performparsing processing on the third TC frame.

With reference to the sixth aspect, in a first possible implementationmanner of the sixth aspect, the apparatus further includes adescrambling module configured to perform descrambling on the second TCframe.

With reference to the sixth aspect or the first possible implementationmanner of the sixth aspect, in a second possible implementation mannerof the sixth aspect, the apparatus further includes a decoding moduleconfigured to decode the second TC frame.

With reference to the sixth aspect or any possible implementation mannerof the sixth aspect, in a third possible implementation manner of thesixth aspect, the obtaining module is further configured to discard,according to frame length information of the second TC frame that isidentified by an Alen field in PCBd of the second TC frame, a pseudo GEMframe, to obtain the second TC frame.

With reference to the sixth aspect or any possible implementation mannerof the sixth aspect, in a fourth possible implementation manner of thesixth aspect, the parsing module is further configured to perform bitmapping restoration on the second TC frame, where the bit mappingrestoration refers to restoration of every N bits to one bit, and parsethe restored second TC frame.

According to a seventh aspect, a PON system is provided, including anOLT and an ONU, where the OLT is connected to the ONU using an ODN,where the OLT is the framing apparatus according to the fourth aspect orany possible implementation manner of the fourth aspect, and the ONU isthe deframing apparatus according to the sixth aspect or any possibleimplementation manner of the sixth aspect.

According to an eighth aspect, a framing apparatus is provided, wherethe framing apparatus includes a processor and a memory, where theprocessor is connected to the memory using a bus, an executableinstruction is stored in the memory, and when the processor executes theexecutable instruction, the processor performs the following steps ofgenerating a first TC frame and a second TC frame separately, where adownstream rate of the first TC frame is 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1,performing bit mapping on the second TC frame to generate a third TCframe, where the bit mapping refers to identifying each bit of thesecond TC frame using N bits, and sending the first TC frame and thethird TC frame to an ONU.

With reference to the eighth aspect, in a first possible implementationmanner of the eighth aspect, the processor further performs a step ofperforming first coding on the second TC frame, where the first codingis one of RS (255,239) coding or RS (248,216) coding, LDPC coding, orcascade FEC coding.

With reference to the eighth aspect or the first possible implementationmanner of the eighth aspect, in a second possible implementation mannerof the eighth aspect, the processor further performs a step of insertinga pseudo GEM frame header into the third TC frame.

With reference to the second possible implementation manner of theeighth aspect, in a third possible implementation manner of the eighthaspect, inserting a pseudo GEM frame header into the third TC frameincludes inserting a placeholder into the third TC frame, performingscrambling on the third TC frame into which the placeholder is inserted,and filling the placeholder using the pseudo GEM frame header.

With reference to the third possible implementation manner of the eighthaspect, in a fourth possible implementation manner of the eighth aspect,the processor further performs a step of performing second coding on thefirst TC frame and the third TC frame into which the pseudo GEM frame isinserted, where the second coding is one of RS (255,239) coding or RS(248,216) coding, LDPC coding, or cascade FEC coding.

With reference to the fourth possible implementation manner of theeighth aspect, in a fifth possible implementation manner of the eighthaspect, the processor further performs a step of performing scramblingon the first TC frame and the third TC frame that have undergone thesecond coding.

With reference to the eighth aspect or any possible implementationmanner of the eighth aspect, in a sixth possible implementation mannerof the eighth aspect, a PCBd field of the second TC frame includes afield used to indicate the frame length of the second TC frame.

With reference to the eighth aspect or any possible implementationmanner of the eighth aspect, in a seventh possible implementation mannerof the eighth aspect, the frame length of the first TC frame is aninteger multiple of 239 bytes.

With reference to the eighth aspect or any one of the first to sixthpossible implementation manners of the eighth aspect, in an eighthpossible implementation manner of the eighth aspect, the frame length ofthe first TC frame is an integer multiple of 248 bytes.

According to a ninth aspect, a deframing apparatus is provided, wherethe deframing apparatus includes a processor and a memory, where theprocessor is connected to the memory using a bus, an executableinstruction is stored in the memory, and when the processor executes theexecutable instruction, the processor performs the following steps ofreceiving a downstream data stream, and performing synchronization witha first TC frame in the downstream data stream, where the downstreamdata stream includes the first TC frame and a second TC frame, adownstream rate of the first TC frame is 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1, andobtaining the first TC frame, and parsing the first TC frame.

With reference to the ninth aspect, in a first possible implementationmanner of the ninth aspect, the processor further performs a step ofdescrambling the first TC frame.

With reference to the ninth aspect or the first possible implementationmanner of the ninth aspect, in a second possible implementation mannerof the ninth aspect, the processor further performs a step of discardingthe second TC frame.

With reference to the ninth aspect or any possible implementation mannerof the ninth aspect, in a third possible implementation manner of theninth aspect, the processor further performs a step of decoding thefirst TC frame.

With reference to the second possible implementation manner of the ninthaspect, in a fourth possible implementation manner of the ninth aspect,the processor further performs a step of discarding the second TC frame,and discarding the second TC frame includes discarding the second TCframe according to a Port-ID field of a pseudo GEM frame.

With reference to the fourth possible implementation manner of the ninthaspect, in a fifth possible implementation manner of the ninth aspect,when the Port-ID is different from a Port-ID locally recorded by an ONU,discarding the pseudo GEM frame that carries the Port-ID and bytes thatare after the pseudo GEM frame.

According to a tenth aspect, a deframing apparatus is provided, wherethe deframing apparatus includes a processor and a memory, where theprocessor is connected to the memory using a bus, an executableinstruction is stored in the memory, and when the processor executes theexecutable instruction, the processor performs the following steps ofreceiving a downstream data stream, where the downstream data streamincludes a first TC frame and a second TC frame, where a downstream rateof the first TC frame complies with a standard, a downstream rate of thesecond TC frame is 1/N of the downstream rate of the first TC frame, asum of frame lengths of the first TC frame and the second TC frame is125 μs, and an interval between frame headers of second TC frames is 125μs, where N is an integer greater than 1, obtaining the second TC frame,performing bit mapping restoration on the second TC frame to generate athird TC frame, where the bit mapping restoration refers to restorationof every N bits in the second TC frame to one bit, and parsing the thirdTC frame.

With reference to the tenth aspect, in a first possible implementationmanner of the tenth aspect, the processor further performs a step ofdescrambling the second TC frame.

With reference to the tenth aspect or the first possible implementationmanner of the tenth aspect, in a second possible implementation mannerof the tenth aspect, the processor further performs a step of decodingthe second TC frame.

With reference to the tenth aspect or any possible implementation mannerof the tenth aspect, in a third possible implementation manner of thetenth aspect, the processor is configured to perform the obtaining thesecond TC frame, where obtaining the second TC frame includes removing,according to frame length information of the second TC frame that isindicated by an Alen field in a PCBd field of the second TC frame, apseudo GEM frame field from the received second TC frame to obtain thesecond TC frame.

In the embodiments of the present disclosure, the framing method isprovided on a sending side, and in the framing method, a line ratecorresponding to a second TC frame is lower than a line rate of a firstTC frame such that a rate of a receiver on a receiving side is decreasedand a bandwidth of the receiver is narrowed, thereby decreasing anoptical link loss and increasing an optical power budget.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly describes theaccompanying drawings required for describing the embodiments. Theaccompanying drawings in the following description show merely someembodiments of the present disclosure, and a person of ordinary skill inthe art may still derive other drawings from these accompanying drawingswithout creative efforts.

FIG. 1 is a schematic structural diagram of a GPON network;

FIG. 2A is a schematic structural diagram of a PON network in whichmultiple rates coexist according to an embodiment of the presentdisclosure;

FIG. 2B is a schematic structural diagram of another PON network inwhich multiple rates coexist according to an embodiment of the presentdisclosure;

FIG. 3 is a schematic flowchart of a framing method in a PON accordingto an embodiment of the present disclosure;

FIG. 4A is a schematic structural diagram of a GPON TC (GTC) frameaccording to an embodiment of the present disclosure;

FIG. 4B is a schematic structural diagram of an Ident field of a GTCframe according to an embodiment of the present disclosure;

FIG. 4C is a schematic structural diagram of a data stream consisting ofmultiple GTC frames according to an embodiment of the presentdisclosure;

FIG. 4D is a schematic structural diagram of a GEM frame according to anembodiment of the present disclosure;

FIG. 4E is a schematic structural diagram of a payload length downstream(Plend) field of a GTC frame according to an embodiment of the presentdisclosure;

FIG. 4F is a schematic structural diagram of a a physical (PHY) frameaccording to an embodiment of the present disclosure;

FIG. 5A is a schematic diagram of a first TC frame and a second TC frameaccording to an embodiment of the present disclosure;

FIG. 5B is a schematic diagram of specific structures of a first TCframe and a second TC frame according to an embodiment of the presentdisclosure;

FIG. 6 is a schematic structural diagram of a pseudo GEM frame accordingto an embodiment of the present disclosure;

FIG. 7A is a schematic diagram of framing in a PON according to anembodiment of the present disclosure;

FIG. 7B is a schematic flowchart of another framing method in a PONaccording to an embodiment of the present disclosure;

FIG. 8 is a schematic flowchart of a deframing method in a PON accordingto an embodiment of the present disclosure;

FIG. 9 is a schematic flowchart of another deframing method in a PONaccording to an embodiment of the present disclosure;

FIG. 10 is a schematic structural diagram of a framing apparatus in aPON according to an embodiment of the present disclosure;

FIG. 11 is a schematic structural diagram of another framing apparatusin a PON according to an embodiment of the present disclosure;

FIG. 12 is a schematic structural diagram of a deframing apparatusaccording to an embodiment of the present disclosure;

FIG. 13 is a schematic structural diagram of another deframing apparatusaccording to an embodiment of the present disclosure;

FIG. 14 is a schematic structural diagram of still another deframingapparatus according to an embodiment of the present disclosure; and

FIG. 15 is a schematic structural diagram of yet another deframingapparatus according to an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following clearly and describes the technical solutions in theembodiments of the present disclosure with reference to the accompanyingdrawings in the embodiments of the present disclosure. The describedembodiments are merely some but not all of the embodiments of thepresent disclosure. All other embodiments obtained by a person ofordinary skill in the art based on the embodiments of the presentdisclosure without creative efforts shall fall within the protectionscope of the present disclosure.

A GPON technology complies with an integrated passive optical accessstandard-G.984.3 series made by the ITU-TelecommunicationStandardization Sector (ITU-T), and is characterized by high bandwidth,high efficiency, large coverage, abundant user interfaces, and the like.Currently, there are multiple transmission rates in the GPON technology.1.24416 Gbps in an upstream direction and 2.48832 Gbps in a downstreamdirection are currently most common GPON transmission rates, and arereferred to as upstream 1.244 Gbps and downstream 2.488 Gbps for shortin the following. It is specified in the existing G.984.3 standard thata length of a downstream GTC frame is 125 μs, that is, the downstreamGTC frame includes 38,880 bytes in total, and a length of an upstreamframe is 125 μs, that is, 19,440 bytes.

A GTC layer is defined in the standard G.984.3. The GTC layer may beused as a common transmission platform to bear various customer signalssuch as an ATM signal and a GEM signal. The GTC layer further includes aframing sub-layer and an adaptation sub-layer. The framing sub-layer isused to implement encapsulation of a GTC frame and terminate a requiredODN transmission function and a required particular PON function (suchas ranging and bandwidth allocation). The adaptation sub-layer mainlyprovides an interface between a protocol data unit (PDU) and ahigh-layer entity. Conversion of ATM information and GEM informationbetween a service data unit (SDU) and a PDU is completed at respectiveadaptation sub-layers.

An XG-PON (may also be referred to as 10 G-GPON) indicates a nextgeneration GPON, which is a PON system whose downstream rate reaches 10Gbps. Generally, the 10 G-GPON belongs to a first phase of the nextgeneration PON (NG-PON1) and corresponds to the G.987 series standards,where an asymmetric system (the asymmetric system refers to a systemwhose upstream rate is 2.5 Gbps and downstream rate is 10 Gbps) isreferred to as XG-PON1, and a symmetrical system (the symmetrical systemrefers to a system whose upstream rate is 10 Gbps and downstream rate is10 Gbps) is referred to as XG-PON2. It is specified in the existingstandard G.987 that a downstream XG-PON frame transmitted at a TC layeris referred to as a PHY frame, and a frame length of the PHY frame is125 μs, that is, a downstream PHY frame includes 155,520 bytes in total,of which a quantity is four times as large as a quantity of bytesincluded in the GTC frame in the GPON.

Currently, for the XG-PON1, the ITU-T has made substantive progress, andstandardization of the XG-PON2 is in process. Similarly, the XG-PON1also has a TC layer, which is referred to as an XGTC layer. The TC layerof the XG-PON1 is divided into a service adaptation sub-layer, a framingsub-layer, and a physical adaptation sub-layer. The service adaptationsub-layer mainly covers functions such as encapsulation of an XGEM frameand allocation and filtering of an XGEM-ID, and supports segmentationand recombination of data units and a delineation function of an XGEMframe. The framing sub-layer includes a function such as encapsulationand parsing of an XGTC frame or a burst data frame, an embeddedoperation and administration message (OAM) function, a physical layeroperations, administration and maintenance (PLOAM) function, andfiltering of an allocation identifier (Alloc-ID). The physicaladaptation sub-layer is configured to implement a FEC code function, aline coding function, and a burst data overhead function.

FIG. 2A is a schematic structural diagram of a PON network in whichmultiple rates coexist according to an embodiment of the presentdisclosure. As shown in FIG. 2A, the PON system is a GPON system, andincludes an OLT, an ODN, and at least two ONUs (designated as ONU 1, ONU2, and ONU n). A downstream receive rate of one ONU is 2.488 Gbps, whichis based on a specification of the standard G.984.3, and a downstreamreceive rate of another ONU is 1/N of 2.488 Gbps, where N is an integergreater than 1. For example, in a specific implementation manner, thedownstream receive rate of the ONU may be 1244 Mbps (i.e., 1.244 Gbps)or 622 Mbps. A person of ordinary skill in the art should understandthat in the GPON system, different transmission rates coexist in adownstream direction in a time division manner, and an upstreambandwidth is shared in an upstream direction by means of time divisionmultiplexing (TDM). A benefit of the network structure is that, when anoperator increases an optical power budget of the system, the networkstructure can be compatible with an existing GPON network, that is,reconstruction is performed based on the existing GPON network such thata reconstruction cost is reduced.

FIG. 2B is a schematic structural diagram of another PON network inwhich multiple rates coexist according to an embodiment of the presentdisclosure. As shown in FIG. 2B, the PON system is an XG-PON system, andincludes an OLT, an ODN, and at least two ONUs (designated as ONU 1, ONU2, and ONU n). A downstream receive rate of one ONU is 10 Gbps, which isbased on a specification of the standard G.987.3 (in a strict sense, thedownstream receive rate is four times of 2.488 Gbps, that is, 9.95328Gbps. However, for a person skilled in the art, 9.95328 Gbps is oftenreferred to as 10 Gbps), and a downstream receive rate of another ONU is1/M of 10 Gbps, where M is an integer greater than 1. For example, thedownstream receive rate may be 2.488 Gbps (i.e., 2488 Mbps), or may be4.97664 Gbps. A person of ordinary skill in the art should understandthat in the XG-PON system, different transmission rates coexist in adownstream direction in a time division manner, and an upstreambandwidth is shared in an upstream direction by means of TDM. A benefitof the network structure is that, when an operator increases an opticalpower budget using the method provided in this embodiment of the presentdisclosure, the network structure can be compatible with the deployedXG-PON network, that is, reconstruction is performed based on theexisting XG-PON network such that a reconstruction cost is reduced.

This embodiment of the present disclosure is based on the networkstructures in FIG. 2A and FIG. 2B. For ease of understanding, a generalidea of this embodiment of the present disclosure is to provide anetwork structure in which multiple rates coexist, where the networkstructure in which multiple rates coexist may be implemented byreconstructing a present network. For example, a downstream receive rateof an ONU of a GPON of the present network is 2.488 Gbps, and bydeploying some ONUs whose receive rate is 1/N of 2.488 Gbps in the OLT,the network has ONUs of at least two rates. A particular frame isgenerated on an OLT side, and the particular frame is logically dividedinto two parts, where the two parts are referred to as a first frame anda second frame. A structure of the first frame corresponds to aspecification of an existing standard, and a particular structure isused for a structure of the second frame such that when the particularframe is received on an ONU side, an existing ONU (that is, an ONU whosedownstream receive rate is 2.488 Gbps) of the GPON identifies the firstframe and parses the first frame using the method provided in thisembodiment of the present disclosure. An ONU (that is, an ONU whosedownstream receive rate is 1/N of 2.488 Gbps) that newly joins thenetwork identifies the second frame and parses the second frame usingthe method provided in this embodiment of the present disclosure.Therefore, by means of this method, an optical power budget of an entiresystem is increased without affecting an existing network system. Forspecific content of the present disclosure, refer to specificembodiments.

Embodiment 1

FIG. 3 is a schematic flowchart of a framing method according to anembodiment of the present disclosure. The method is applied in thenetwork structure shown in FIG. 2A or FIG. 2B. As shown in FIG. 3, themethod includes the following steps.

Step S301: Generate a first TC frame and a second TC frame separately,where a downstream rate of the first TC frame complies with aspecification of the standard G.984.3 or G.987.3, a downstream rate ofthe second TC frame is 1/N of the downstream rate of the first TC frame,and a sum of frame lengths of the first TC frame and the second TC frameis 125 μs, where N is an integer greater than 1 and the downstream rateof the first TC frame is 2.488 Gbps or 10 Gbps.

Step S302: Perform bit mapping on the second TC frame to generate athird TC frame, where the bit mapping refers to identifying each bit ofthe second TC frame using N bits.

Step S303: Send the first TC frame and the third TC frame to an ONU.

A value of N is one of 2, 4, or 8.

An interval between frame headers of second TC frames is also 125 μs.

In this embodiment of the present disclosure, further, if the first TCframe and the second TC frame are applied in a GPON system, a structureof the first TC frame is similar to a structure of a GTC frame definedin the existing standard G.984.3, where both the structures include aPCBd field and a payload field, but have different total quantities ofbytes. For details, refer to the following description. If the first TCframe and the second TC frame are applied in an XG-PON system, astructure of the first TC frame is similar to a structure of a PHY framedefined in the existing standard G.987.3, where both the structuresinclude a PCBd field and a payload field, but have different totalquantities of bytes. For details, refer to the following description.This embodiment of the present disclosure is further described below indetail by separately using the GPON system and the XG-PON system.

The structure of the GTC frame is shown in FIG. 4A to FIG. 4E, andconsists of a PCBd part and a GTC payload (designated as GTC Payload)part. The PCBd consists of the following fields.

A physical synchronization field designated as Psync, which has fourbytes in total, is located at a start position of each PCBd, and is usedfor frame synchronization, that is, the ONU determines a start positionof a downstream frame according to the Psync;

An Ident field, which has four bytes in total, and is used to identifyindication information of a frame structure, where for a specificstructure of the Ident field, refer to FIG. 4B, where a highest 1 bit isused to indicate a downstream FEC state (designated as FEC ind), and low30 bits are a superframe counter;

A PLOAM downstream field designated as PLOAMd, which has 13 bytes intotal, and is used to carry a downstream PLOAM message to completemanagement functions such as ONU activation, encryption configuration,key management, and alarm notification, where for a specific structureof the PLOAM message, refer to a specification in the standard G.984.3,and details are not described herein again;

A bit interleaved parity (BIP) field, which has one byte in total, andis used to perform BIP on all bytes (except an FEC parity field) after aBIP field of a previous GTC frame, where BIP information carried in theBIP field covers all transmission bytes except an FEC parity bit (if FECparity exists). After FEC is completed (if the FEC parity exists), areceive end should calculate BIP values of all received bytes after theprevious BIP field, where the received bytes should not cover an FECparity bit, and compare the BIP values with a received BIP value inorder to estimate a quantity of errors on a link;

A Plend, which has four bytes in total, where to ensure robustness, thePlend field is transmitted twice. A specific structure is shown in FIG.4E. The Plend field mainly includes a bandwidth mapping length (Blen)field and an Alen field, where the Blen field is used to indicate aquantity of bandwidth bitmap (BWmap) bytes, the Alen field is used toindicate a length of an ATM block, and because the Alen field is notused in the GPON standard G.984, default values of all bits in the Alenfield are 0; and

An upstream BWmap (designated as Upstream BWmap) field, where a lengthof the field is variable, the Blen field is used to indicate quantityinformation of the field, and a length of each BWmap is eight bytes.

As shown in FIG. 4C, a GTC payload consists of several GEM frames. Asshown in FIG. 4D, the GEM frame consists of a frame header (designatedas GEM Header) and a payload (designated as GEM Payload).

FIG. 4B to FIG. 4E show specific content of the fields of the GTC frame,and for a specific definition of the GTC frame, refer to the descriptionin the standard G.984.3, and details are not described herein again.

It should be noted that in Embodiment 1 of the present disclosure, whenthe first TC frame and the second TC frame are applied in the GPONsystem, specific structures of the first TC frame and the second TCframe are similar to the structure of the foregoing GTC frame, where allthe structures include PCBd and a payload field. However, in thisembodiment of the present disclosure, a sum of frame lengths of thefirst TC frame and the second TC frame is 125 μs, and a quantity ofbytes of the first TC frame or the second TC frame is less than aquantity of bytes of the GTC frame, that is, in this embodiment of thepresent disclosure, a length of the payload field of the first TC frameor the second TC frame is less than a length of the payload field of theGTC frame.

It should be further noted that in Embodiment 1 of the presentdisclosure, an Alen field in a Plend field of the first TC framecomplies with a specification in the other approaches, and a defaultvalue of the Alen field is 0. However, an Alen field of the second TCframe is used to indicate a frame length of the second TC frame.

The GPON is used as an example. In this embodiment of the presentdisclosure, the sum of the frame lengths of the first TC frame and thesecond TC frame is 125 μs, the downstream rate of the first TC frame is2.488 Gbps, and the downstream rate of the second TC frame is 1/N of2.488 Gbps, for example, 622 Mbps. Further, a quantity of bytes of thefirst TC frame and a quantity of bytes of the second TC frame may beobtained by calculating the frame lengths of the two frames. Forexample, assuming that the frame length of the first TC frame is 60.7 μsand the frame length of the second TC frame is 64.3 μs, the frame lengthof the first TC frame is 18,880 bytes and the second TC frame is 5,000bytes. Certainly, the frame length of the first TC frame and the framelength of the second TC frame may be specified by an OLT, and this isnot limited in this embodiment of the present disclosure.

It should be understood that, an example in which the frame length ofthe first TC frame is 18,880 bytes is used. A quantity of bytes occupiedby the PCBd of the first TC frame is the same as that of an existing GTCframe, but a quantity of bytes occupied by a payload part of the firstTC frame is less than a quantity of bytes of the payload of the GTCframe that is specified in the standard.

For the XG-PON system, a framing sub-layer of a TC layer is responsiblefor generating the first TC frame and the second TC frame. A framestructure of the first TC frame or the second TC frame is similar to thestructure of the PHY frame that is defined in the existing standardG.987.3. For details, refer to the following description. The structureof the PHY frame is shown in FIG. 4F, and a downstream PHY frameconsists of a PCBd and a payload part (designated as Payload) of the PHYframe, where the PCBd consists of the following fields:

A Psync field, which occupies eight bytes (designated as 8B) and has 64bits in total, is located at a start position of each PCBd, and is usedfor frame synchronization, that is, the ONU determines a start positionof a downstream frame according to the Psync, where a value of the fieldis set to 0xC5E5 1840 FD59 BB49;

A superframe counter (designated as SFC) field, which occupies eightbytes (designated as 8B), has 64 bits in total, and includes a 51-bitsuperframe counter and a 13-bit header error control (HEC) field (notshown), where as compared with a previous PHY frame, a value of an SFCof each PHY frame is increased, when a value of an SFC of a PHY framereaches a maximum value, an SFC of a next PHY frame is calculated from0. For specific content, refer to description in the standard G.987.3,and details are not described herein again; and

A PON-ID field, including 51-bit PON identification information and a13-bit HEC field, where a PON-ID is set by the OLT, and a default valueof the PON-ID is 51 zeros.

The payload part of the PHY frame is used to bear an XGTC frame, wherethe XGTC frame consists of an XGTC frame header (designated as XTGCHeader) and an XGTC payload. The XGTC frame header includes threesubfields, which are sequentially Hlend of 4 bytes, BWmap of N*8bytes,and PLOAMd of P*48bytes. The payload of the XGTC frame bears multipleXGEM frames, where an XGEM frame consists of an XGEM header of 8 bytesand an XGEM payload L bytes. The XGEM header includes six fields, whichare sequentially Payload Length Indicator (PLI) of 14 bits, Key index of2 bits, Port-ID of 16 bits, options of 18 bits, LF of 1 bit, and HEC of13 bits. For meanings of the fields, refer to the description in thestandard G.987.3, and details are not described herein again.

As shown in FIG. 5A or FIG. 5B, the sum of the frame lengths of thefirst TC frame (designated as TC-1 subframe) and the second TC frame(designated as TC-2 subframe) is 125 μs, and an interval between frameheaders of second TC frames is 125 μs. The XG-PON is used as an example.In this embodiment of the present disclosure, the sum of the framelengths of the first TC frame and the second TC frame is 125 μs, thedownstream rate of the first TC frame is 10 Gbps, and the downstreamrate of the second TC frame is 2.488 Gbps. Further, a quantity of bytesof the first TC frame and a quantity of bytes of the second TC frame maybe obtained by calculating the frame lengths of the two frames. Forexample, assuming that the frame length of the first TC frame is 60.7 μsand the frame length of the second TC frame is 64.3 μs, the frame lengthof the first TC frame is 75,520 bytes and the second TC frame is 20,000bytes. Certainly, the frame length of the first TC frame and the framelength of the second TC frame may be specified by the OLT, and this isnot limited in this embodiment of the present disclosure.

It should be understood that, in an example in which the frame length ofthe first TC frame is 75,520 bytes, a quantity of bytes occupied by thePCBd of the first TC frame is the same as that of an existing PHY frame,but a quantity of bytes occupied by a payload part of the first TC frameis less than a quantity of bytes of the payload of the PHY frame that isspecified in the standard. It should be noted that in a framing process,the OLT multiplexes existing logic at a TC adaptation layer, and thefirst TC frame and the second TC frame are separately generated at aframing sub-layer, and values of BIP fields of the first TC frame andthe second TC frame are separately calculated.

It should be noted that, for the second TC frame, a calculation range ofa first BIP of the second TC frame is data from a frame header of thesecond TC frame to the BIP field, and a calculation range of another BIPis data of the second TC frame after a BIP field of a previous second TCframe and before the BIP field of the current second TC frame.

For the first TC frame, the BIP field protects data of an entire TCframe (including the first TC frame and the second TC frame), that is,data obtained after the first TC frame and the second TC frame aremapped to the rate of 2.488 Gbps. A value of a BIP field of an N*1 firstTC frame is generated according to a BIP calculation method using thefollowing three parts a part after a BIP field of an (N−1)^(th) first TCframe, an (N−1)^(th) second TC frame, and a part before the BIP field ofthe N^(th) first TC frame.

For example, a BIP value of a 2^(nd) first TC frame is based on a partafter a BIP field of a 1^(st) first TC frame, a 1^(st) second TC frame,and a part before a BIP field of the 2^(nd) first TC frame, and so on.

For specific content of step 302, the GPON is used as an example fordescription. The second TC frame corresponds to a rate of 1/N of 2.488Gbps. In an example in which a line rate of the second TC frame is 622Mbps, for accurate timing, a bit width of the second TC frame is N timesas large as that of a first TC frame. As shown in this embodiment of thepresent disclosure, the rate of the second TC frame is 622 Mbps, whichoccupies 5,000 bytes (which is obtained by calculating based on theassumption that the frame length of the first frame is 60.7 μs and theframe length of the second frame is 64.7 μs) in total. Because adownstream processing rate of a transmitter of an existing OLT is 2.488Gbps, before the second TC frame is transmitted, a downstream framewhose downstream rate is 622 Mbps needs to be mapped to a downstreamframe whose rate is 2.488 Gbps, that is, a third TC frame. A framelength of the third TC frame is 5,000*4=20,000 bytes such that a totalquantity of bytes of the first TC frame and the third TC frame is18,880+20,000=38,880 bytes, which is exactly a total quantity of bytesof the TC frame of the GPON in the other approaches.

Further, a specific implementation method for identifying one bit usingfour bits is as follows. For example, a bit “1” is mapped to “1100”, anda bit “0” is mapped to “0011”. Certainly, another mapping method mayalso be used, for example, a bit “1” is mapped to “1111”, and a bit “0”is mapped to “0000”, as long as four bits to which 0 is mapped and fourbits to which 1 is mapped represent different values. Certainly, if thesecond TC frame corresponds to 311 Mbps, 1244 Mbps, or another ratelower than 2.488 Gbps, the bit width of the second TC frame is aninteger multiple of that of the first TC frame. For example, the bitwidth of the second TC frame is eight times or two times as large asthat of first TC frame. Correspondingly, a specific implementationmanner of bit mapping is identifying one bit using eight bits. Forexample, a bit “1” is mapped to “11110000”, and a bit “0” is mapped to“00001111”. Alternatively, two bits are used to identify one bit. Forexample, a bit “1” is mapped to “11”, and a bit “0” is mapped to “00”.

In this embodiment of the present disclosure, for the GPON, the framelength of the third TC frame and the frame length of the first TC frameare 38,880 bytes in total, and the 38,880 bytes are transmitted, as awhole, to an optical transmitter using a media access control (MAC)module of the OLT, and the optical transmitter transmits the 38,880bytes to multiple ONUs.

A person of ordinary skill in the art should understand that, for theXG-PON system, the bit mapping is performed on the second TC frame, anda principle and a process of the bit mapping are the same as that in theforegoing description of the GPON system. A person of ordinary skill inthe art may learn, without any creative effort, how to perform bitmapping in the XG-PON system according to the foregoing description ofthe GPON.

It should be understood that, for the XG-PON, the frame length of thethird TC frame and the frame length of the first TC frame are 155,520bytes in total, and the 155,520 bytes are transmitted, as a whole, to anoptical transmitter using a MAC module of the OLT, and the opticaltransmitter transmits the 155,520 bytes to multiple ONUs.

In this embodiment of the present disclosure, preferably, the framelength of the first TC frame is an integer multiple of 239 bytes.Further, in the GPON system, if the frame length of the first TC frameis an integer multiple of 239 bytes, in this embodiment of the presentdisclosure, an FEC coding procedure of the first TC frame may besimplified such that a solution for processing FEC decoding by an ONUwhose receive rate is 2.488 Gbps is the same as a solution in the otherapproaches.

In this embodiment of the present disclosure, preferably, the framelength of the first TC frame is an integer multiple of 248 bytes.Further, in the XG-PON system, if the frame length of the first TC frameis an integer multiple of 248 bytes, in this embodiment of the presentdisclosure, an FEC coding procedure of the first TC frame may besimplified such that a solution for processing FEC decoding by an ONUwhose receive rate is 10 Gbps is the same as a solution in the otherapproaches.

Before step S302, the method further includes the following step.

Step S301 a: Perform scrambling on the second TC frame.

Further, a scramble pattern (SP) used by a current second TC frame iscalculated using a value of an Alen field of a previous second TC frame,where the Alen field is used to indicate the frame length of the secondTC frame. For a specific scrambling method, refer to a scramblingtechnology existing in other approaches, and details are not describedherein again.

Before step S302, the method further includes the following step.

Step S301 b: Perform first coding on the second TC frame.

Further, the first coding may be RS (255,239) coding, RS (248,216)coding, LDPC coding, or cascade FEC coding, or another FEC codingrecorded in the other approaches, and if a high-order coding manner isused, a coding gain may be obtained, and details are not describedherein again.

Before step S303, the method further includes the following step.

Step S301 c: Insert a frame header of a pseudo GEM frame into the thirdTC frame. A beneficial effect of the step is that an original ONU (theoriginal ONU refers to an ONU whose receive rate is 2.488 Gbps in theGPON system, or an ONU whose receive rate is 10 Gbps in the XG-PON) maynot generate a GEM frame loss alarm when receiving the third TC frame.

The step S301 c further includes the following steps.

Step S301 c 1: Insert a placeholder into the third TC frame.

The placeholder means occupying a particular position and then addingspecific content to the particular position. For ease of description,for the GPON system, the ONU whose receive rate is 2.488 Gbps is namedthe original ONU, and an ONU whose receive rate is lower than 2.488 Gbpsis a new ONU. The frame header of the pseudo GEM frame is inserted intothe third TC frame according to a particular rule.

A frame structure of the pseudo GEM frame is shown in FIG. 6. The pseudoGEM is a 5-byte GEM frame header plus an X-byte filler (X is an integergreater than or equal to 0, which may be arbitrarily set by the OLT),and a length of a pseudo GEM frame payload is L bytes. A value of a PLIfield in the pseudo GEM frame header is L+X bytes. A GEM Port-ID of apseudo GEM frame header that is to be inserted is set to a particularidentifier such that the original ONU cannot identify the Port-ID afterreceiving the pseudo GEM frame header carrying the particular Port-ID,but directly discards the pseudo GEM frame header without performingparsing. The new ONU can discard the pseudo GEM frame header and reservecontent of a third TC frame after receiving the third TC frame intowhich the pseudo GEM frame header is inserted.

Further, a placeholder of a first pseudo GEM frame header is insertedafter the first TC frame and before the third TC frame to construct afirst pseudo GEM frame, and similarly, a second pseudo GEM frame is thenconstructed. A value of L should satisfy that a relative small value isselected between a maximum value of a PLI field of the pseudo GEM frameheader and a frame length that is estimated, according to first FECcode, for the third TC frame that is not encapsulated into the pseudoGEM frame, and a value of a frame length of an entire pseudo GEM frame,that is, L+X+5, is required to be an integer multiple of a codewordlength of the first FEC code. The entire pseudo GEM frame includes theinserted pseudo GEM frame header, a fragment of the third TC frame thathas undergone the bit mapping, and a parity bit of the first FEC code.The fragment of the third TC frame is obtained by fragmenting the thirdTC frame according to a data payload length of a first FEC codeword,where a length of the last fragment may be less than a payload length ofone codeword, and for the FEC, refer to existing processing ofshortening a codeword.

Step S301 c 2: Perform scrambling on the third TC frame into which theplaceholder is inserted.

Step S301 c 3: Fill the placeholder using the pseudo GEM frame header.

The pseudo GEM frame header is used to replace the placeholder, and BIPcalculation is performed on the pseudo GEM frame header and a fragmentof the scrambled third TC frame, and a result of the BIP calculation isused to calculate a BIP value of a next first TC frame.

The method further includes the following step.

Step S301 d: Perform second coding on the first TC frame and the thirdTC frame into which the pseudo GEM frame header is inserted, where thesecond coding is one of RS (255,239) coding, RS (248,216) coding, LDPCcoding, or cascade FEC coding. A beneficial effect of step S301 d isthat the original ONU may not generate an FEC alarm when receiving thethird TC frame.

The method further includes the following step.

Step S301 e: Perform third scrambling processing on the first TC frameand the third TC frame that have undergone the second coding.

In this embodiment of the present disclosure, the framing method isprovided on a sending side, and in the framing method, a line ratecorresponding to a second TC frame is lower than a line rate of a firstTC frame such that a rate of a receiver on a receiving side is decreasedand a bandwidth of the receiver is narrowed, thereby decreasing anoptical link loss and increasing an optical power budget.

Embodiment 2

The following describes a framing method in a PON according to anembodiment of the present disclosure in detail with reference to FIGS.7A and 7B. As shown in FIG. 7B, FIG. 7B shows a framing method accordingto this embodiment of the present disclosure. The method includes thefollowing steps.

Step S701: Generate a first TC frame and a second TC frame separately,where a downstream rate of the first TC frame is 2.488 Gbps or 10 Gbps,a downstream rate of the second TC frame is 1/N of the downstream rateof the first TC frame, and a sum of frame lengths of the first TC frameand the second TC frame is 125 μs, where N is an integer greater than 1.

Step S702: Perform first coding on the second TC frame, where the firstcoding may be RS (255,239), or may be another coding manner such as RS(255,151) coding, RS (248,216) coding, LDPC coding, cascade FEC coding,or another FEC coding existing in the other approaches, and details arenot described herein again.

Step S703: Perform scrambling on the second TC frame. Scrambling is sameas in the other approaches, that is, an SP used by the current second TCframe is calculated using a value of an Alen field in a previous secondTC frame.

Step S704: Perform bit mapping on the second TC frame to generate athird TC frame, where the bit mapping refers to identifying each bit ofthe second TC frame using N bits. Further, the second TC framecorresponds to a rate of 1/N of 2.488 Gbps. In an example in which aline rate of the second TC frame is 622 Mbps, for accurate timing, a bitwidth of the second TC frame is N times as large as that of the first TCframe. As shown in this embodiment of the present disclosure, the rateof the second TC frame is 622 Mbps, which occupies 5,000 bytes (which isobtained by calculating based on the assumption that the frame length ofthe first frame is 60.7 μs and the frame length of the second frame is64.3 82 s) in total. Because a downstream processing rate of atransmitter of an existing OLT is 2.488 Gbps, before the second TC frameis transmitted, the bit mapping needs to be performed, that is, adownstream frame whose rate is 622 Mbps is mapped to a downstream framewhose rate is 2.488 Gbps. A frame length of the third TC frame obtainedafter the mapping is 5,000*4=20,000 bytes such that a total quantity ofbytes of the first TC frame and the third TC frame is18,880+20,000=38,880 bytes, which is exactly a total quantity of bytesof a GTC frame of a GPON in the other approaches.

Step S705: Insert a placeholder into the third TC frame.

Step S706: Perform second scrambling on the third TC frame into whichthe placeholder is inserted.

Step S707: Fill a corresponding placeholder using a pseudo GEM frameheader.

Step S708: Perform second coding on the first TC frame and the third TCframe into which the pseudo GEM frame header is inserted, the first TCframe and the third TC frame being a whole, where the second coding maybe RS (255,239) coding, or may be another coding manner such as RS(255,151) coding, RS (248,216) coding, LDPC coding, cascade FEC coding,or another FEC coding existing in the other approaches, and details arenot described herein again.

For detailed description of step S705 to step S708, refer to thedescription in Embodiment 1, and details are not described herein again.

Step S709: Perform scrambling on the first TC frame and the third TCframe that have undergone the second coding.

Step S710: Send the scrambled first TC frame and the scrambled third TCframe as a whole to an ONU.

It should also be understood that sequence numbers of the foregoingprocesses do not mean execution sequences in various embodiments of thepresent disclosure. The execution sequences of the processes should bedetermined according to functions and internal logic of the processes,and should not be construed as any limitation on the implementationprocesses of the embodiments of the present disclosure.

In this embodiment of the present disclosure, the framing method isprovided on a sending side, and in the framing method, a line ratecorresponding to a second TC frame is lower than a line rate of a firstTC frame such that a rate of a receiver on a receiving side is decreasedand a bandwidth of the receiver is narrowed, thereby decreasing anoptical link loss and increasing an optical power budget.

Embodiment 3

FIG. 8 is a schematic flowchart of a deframing method in a PON accordingto an embodiment of the present disclosure. The method may be applied ina GPON or an XG-PON. When the method is applied in a GPON system, themethod is performed by an ONU whose receive rate is 2.488 Gbps. When themethod is applied in an XG-PON system, the method is performed by an ONUwhose receive rate is 10 Gbps. As shown in FIG. 8, the method includesthe following steps.

Step S801: Receive a downstream data stream, where the downstream datastream includes a first TC frame and a second TC frame, where adownstream rate of the first TC frame complies with a specification ofthe standard G.984.3 or G.987, that is, 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1.

Step S802: Perform synchronization with the first TC frame.

Step S803: Parse the first TC frame.

A value of N is one of 2, 4, or 8.

An interval between frame headers of second TC frames is also 125 μs.

The method further includes the following steps (not shown).

Step S801 a: Perform descrambling on the first TC frame.

Step S801 b: Decode the first TC frame.

Step S801 c: Discard the second TC frame.

In this embodiment of the present disclosure, performing synchronizationwith the first TC frame includes performing synchronization with thefirst TC frame according to a Psync field in PCBd of the first TC frame.For details about how to perform synchronization with the first TC frameaccording to the Psync, refer to description in the other approaches,and details are not described herein.

A person of ordinary skill in the art should understand that an opticalreceiver of the ONU receives, using a line, a data stream sent by anOLT, and the data stream is transmitted to a MAC module of the ONU forprocessing. The deframing method provided in this embodiment of thepresent disclosure is performed by the MAC module of the ONU.

It should be understood that the deframing method provided in thisembodiment of the present disclosure and a framing method provided inanother embodiment of the present disclosure correspond to a receivingside and a sending side, respectively. When scrambling is performed onthe sending side, correspondingly, descrambling needs to be performed onthe receiving side, where the descrambling and the scrambling aremutually inverse operations. For a specific technology of the scramblingor the descrambling, refer to description in the other approaches, anddetails are not described herein again.

It should be understood that the deframing method provided in thisembodiment of the present disclosure and the framing method provided inthe other embodiment of the present disclosure correspond to a receivingside and a sending side, respectively. If coding is performed on thesending side, correspondingly, decoding processing needs to be performedon the receiving side, where the decoding and the coding are mutuallyinverse operations.

In this embodiment of the present disclosure, discarding the second TCframe includes discarding the second TC frame according to a Port-IDfield of a frame header of a pseudo GEM frame. A person of ordinaryskill in the art should understand that the MAC module reads a GEMaccording to the Port-ID in the frame header of the GEM frame. Becausethe Port-ID in the pseudo GEM frame does not belong to any ONU, the ONUcannot parse the second TC frame and directly discards the second TCframe. Further, when the MAC module of the ONU determines that thePort-ID is different from a Port-ID locally recorded by the ONU, the MACmodule of the ONU discards the pseudo GEM frame header and the second TCframe that is after the pseudo GEM frame header.

In this embodiment of the present disclosure, the deframing method isprovided on a sending side. In the deframing method, a line ratecorresponding to a second TC frame is lower than a line rate of a firstTC frame such that compared with the other approaches, a rate of areceiver on a receiving side is decreased and a bandwidth of thereceiver is narrowed, thereby decreasing an optical link loss andincreasing an optical power budget.

Embodiment 4

FIG. 9 is a schematic flowchart of another deframing method in a PONaccording to an embodiment of the present disclosure. The method may beapplied in a GPON or an XG-PON. When the method is applied in a GPONsystem, the method is performed by an ONU whose receive rate is 1/N of2.488 Gbps. When the method is applied in an XG-PON system, the methodis performed by an ONU whose receive rate is 1/N of 10 Gbps. As shown inFIG. 9, the method includes the following steps.

Step S901: Receive a downstream data stream, where the downstream datastream includes a first TC frame and a second TC frame, where adownstream rate of the first TC frame is 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1.

Step S902: Obtain the second TC frame.

Step S903: Perform bit mapping restoration on the second TC frame togenerate a third TC frame, where the bit mapping restoration refers torestoration of every N bits in the second TC frame to one bit.

Step S904: Parse the third TC frame.

Optionally, the method further includes the following steps (not shown).

Step S902 a: Perform descrambling on the second TC frame.

Step S902 b: Decode the second TC frame.

In this embodiment of the present disclosure, an optical receiver of theONU receives a downstream data stream, and the downstream data stream istransmitted to a MAC module of the ONU for processing, and the MACmodule receives the downstream data stream and parses the downstreamdata stream. When the MAC module identifies a Psync field in a PCBdfield of the second TC frame, the MAC module performs synchronizationwith the second TC frame according to the Psync field in the PCBd field.

Obtaining the second TC frame includes removing, according to framelength information of the second TC frame that is indicated by an Alenfield in a PCBd field of the second TC frame, a pseudo GEM frame fromthe received second TC frame, to obtain the second TC frame.

A person of ordinary skill in the art should understand that bit mappingis performed on the second TC frame on a sending side, and the second TCframe needs to be restored on a receiving side, that is, the bit mappingand the bit mapping restoration are mutually inverse operations.

A person of ordinary skill in the art should understand that thedeframing method provided in this embodiment of the present disclosureand a framing method provided in another embodiment of the presentdisclosure correspond to a receiving side and a sending side,respectively. When scrambling is performed on the sending side,correspondingly, descrambling needs to be performed on the receivingside, where the descrambling and the scrambling are mutually inverseoperations. For details about the scrambling or the descrambling, referto description in the other approaches, and details are not describedherein again.

A person of ordinary skill in the art should understand that thedeframing method provided in this embodiment of the present disclosureand the framing method provided in the other embodiment of the presentdisclosure correspond to a receiving side and a sending side,respectively. If coding is performed on the sending side,correspondingly, decoding processing needs to be performed on thereceiving side, where the decoding and the coding are mutually inverseoperations.

In this embodiment of the present disclosure, the deframing method isprovided on a receiving side. In the deframing method, a line ratecorresponding to a second TC frame is lower than a line rate of a firstTC frame such that a rate of a receiver on a receiving side is decreasedand a bandwidth of the receiver is narrowed, thereby decreasing anoptical link loss and increasing an optical power budget.

Embodiment 5

FIG. 10 is a schematic structural diagram of a framing apparatus 1000 ina PON according to an embodiment of the present disclosure. Referring toFIG. 10, the apparatus 1000 includes a generation module 1010 configuredto generate a first TC frame and a second TC frame separately, where adownstream rate of the first TC frame complies with a specification ofthe standard G.984.3 or G.987.3, a downstream rate of the second TCframe is 1/N of the downstream rate of the first TC frame, and a sum offrame lengths of the first TC frame and the second TC frame is 125 μs,where N is an integer greater than 1, a mapping module 1020 configuredto perform bit mapping on the second TC frame to generate a third TCframe, where the bit mapping refers to identifying each bit of thesecond TC frame using N bits, and a sending module 1030 configured tosend the first TC frame and the third TC frame to an ONU.

Optionally, the apparatus 1000 further includes a scrambling module (notshown), where the scrambling module is configured to perform scramblingon the second TC frame.

Optionally, the apparatus 1000 further includes a coding module (notshown), where the coding module is configured to perform first coding onthe second TC frame, where the first coding is one of RS (255,239)coding, RS (248,216) coding, LDPC coding, or cascade FEC coding.

Optionally, the apparatus 1000 further includes a processing module (notshown), where the processing module is configured to insert a pseudo GEMframe header into the third TC frame.

The processing module is further configured to insert a placeholder intothe third TC frame, perform scrambling on the third TC frame into whichthe placeholder is inserted, and fill the placeholder using the pseudoGEM frame header.

Optionally, the coding module is further configured to perform secondcoding on the first TC frame and the third TC frame into which thepseudo GEM frame header is inserted, where the second coding is one ofRS (255,239) coding, RS (248,216) coding, LDPC coding, or cascade FECcoding.

Optionally, the scrambling module is further configured to performscrambling on the first TC frame and the third TC frame that haveundergone the second coding.

It should be noted that specific actions performed by modules inEmbodiment 5 are steps in the method in Embodiment 1 or 2 above, and thespecific actions and the steps have a same effect. Details are notdescribed herein again.

By means of the framing apparatus 1000 in a PON according to thisembodiment of the present disclosure, a line rate corresponding to asecond TC frame generated by the apparatus 1000 is lower than a linerate of a first TC frame such that compared with the other approaches, arate of a receiver on a receiving side is decreased and a bandwidth ofthe receiver is narrowed, thereby decreasing an optical link loss andincreasing an optical power budget.

Further, the framing apparatus 1000 may be a MAC processing module of anOLT. For example, for the MAC processing module, a field programmablegate array (FPGA), an application specific integrated circuit (ASIC), aSystem-On-a-Chip (SoC), a central processing unit (CPU), a networkprocessor (NP), a digital signal processing circuit (DSP), a microcontroller unit (MCU), a programmable logic controller (PLD), or anotherintegrated chip may be used.

FIG. 11 is a schematic structural diagram of a framing apparatus 1100according to an embodiment of the present disclosure. Referring to FIG.11, the apparatus 1100 includes a processor 1110, a memory 1120, acommunications bus 1130, and a communications interface 1140. Theprocessor 1110, the memory 1120, and the communications interface 1140are connected to and communicate with each other using thecommunications bus 1130. The communications bus 1130 may be an industrystandard architecture (ISA) bus, a peripheral component interconnect(PCI) bus, an extended ISA (EISA) bus, or the like. The communicationsbus 1130 may be classified into an address bus, a data bus, a controlbus, and the like. For convenience of representation, the communicationsbus 1130 is represented by only one bold line in FIG. 11, but it doesnot represent that there is only one bus or one type of bus. Theprocessor 1110 may be a single-core or multi-core CPU, an ASIC, or isconfigured as one or more integrated circuits implementing thisembodiment of the present disclosure. The memory 1120 may be a read-onlymemory (ROM) or another type of a static storage device that can storestatic information and an instruction, a random access memory (RAM) oranother type of a dynamic storage device that can store information andan instruction, or may be an electrically erasable programmable ROM(EEPROM), a compact disc ROM (CD-ROM) or another optical disc storage,optical disc storage (including a compact optical disc, a laser disc, anoptical disc, a digital versatile disc (DVD), a BLU-RAY DISC, and thelike), a magnetic disk storage medium or another magnetic storagedevice, or any other medium that can be used to carry or store expectedprogram code in an instruction or data structure form and that can beaccessed by a computer. The present disclosure does not limit thereto.The memory 1120 is configured to store a computer executableinstruction. Further, the computer executable instruction may includeprogram code.

The processor 1110 runs the computer executable instruction, andfurther, the processor 1110 is configured to perform the method stepsdescribed in Embodiment 1 or Embodiment 2.

Further, the framing apparatus 1100 may be a MAC processing module of anOLT. For example, the MAC processing module may be an FPGA, an ASIC, anSoC, or a CPU, an NP, a DSP, an MCU, a PLD, or another integrated chip.

Embodiment 6

FIG. 12 is a schematic structural diagram of a deframing apparatus 1200in a PON according to an embodiment of the present disclosure. Referringto FIG. 12, the apparatus 1200 includes a receiving module 1210configured to receive a downstream data stream, where the downstreamdata stream includes a first TC frame and a second TC frame, where adownstream rate of the first TC frame is 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1, asynchronization module 1220 configured to perform synchronization withthe first TC frame, and a parsing module 1230 configured to parse thefirst TC frame.

Optionally, the apparatus 1200 further includes a descrambling module(not shown), where the scrambling module is configured to performdescrambling on the first TC frame.

Optionally, the apparatus 1200 further includes a decoding module (notshown) configured to perform first decoding on the first TC frame.

Optionally, the apparatus 1200 further includes a discarding module (notshown) configured to discard the second TC frame.

In this embodiment of the present disclosure, performing synchronizationwith the first TC frame includes receiving the downstream data frame andparsing the downstream data frame, and performing synchronization withthe first TC frame according to a Psync field in PCBd of the first TCframe, where for details about how to perform synchronization with thefirst TC frame according to the Psync, refer to description in the otherapproaches, and details are not described herein again.

Further, the discarding module is further configured to discard thesecond TC frame according to a Port-ID field of a pseudo GEM frame, anddiscard the pseudo GEM frame carrying the Port-ID and the second TCframe that is after the pseudo GEM frame when the Port-ID is differentfrom a Port-ID locally recorded by an ONU.

A person of ordinary skill in the art should understand that an opticalreceiver of an ONU receives, using a line, a data stream sent by an OLT,and the data stream is transmitted to a MAC module of the ONU forprocessing. The deframing method provided in this embodiment of thepresent disclosure is further performed by the MAC module of the ONU.

It should be understood that the deframing apparatus provided in thisembodiment of the present disclosure and a framing apparatus provided inanother embodiment of the present disclosure correspond to a receivingside and a sending side, respectively. When scrambling is performed onthe sending side, correspondingly, descrambling needs to be performed onthe receiving side, where the descrambling and the scrambling aremutually inverse operations. For a specific technology of the scramblingor the descrambling, refer to description in the other approaches, anddetails are not described herein again.

It should be noted that specific actions performed by modules inEmbodiment 6 are steps in the method in Embodiment 3 above, and thespecific actions and the steps a same effect. Details are not describedherein again.

FIG. 13 is a schematic structural diagram of a deframing apparatus 1300according to an embodiment of the present disclosure. Referring to FIG.13, the apparatus 1300 includes a processor 1310, a memory 1320, acommunications bus 1330, and a communications interface 1340. Theprocessor 1310, the memory 1320, and the communications interface 1340are connected to and communicate with each other using thecommunications bus 1330. The processor 1310 may be a single-core ormulti-core CPU, or an ASIC, or is configured as one or more integratedcircuits implementing this embodiment of the present disclosure. Thememory 1320 may be a high-speed RAM, or may be a non-volatile memory,for example, a flash memory, or at least one magnetic disk storage. Thememory 1320 is configured to store a computer executable instruction.Further, the computer executable instruction may include program code.

The processor 1310 runs the computer executable instruction, andfurther, the processor 1310 is configured to perform the method stepsdescribed in the method in Embodiment 3.

Further, in terms of physical entities, for the deframing apparatus, anFPGA, an ASIC, an SoC, a CPU, an NP, a DSP, an MCU, a PLC, or anotherintegrated chip may be used.

In this embodiment of the present disclosure, a deframing apparatus isprovided on a receiving side, and in a downstream data stream receivedby the apparatus, a line rate corresponding to a second TC frame islower than a line rate of a first TC frame such that compared with adownstream rate in the other approaches, in this embodiment of thepresent disclosure, a rate of a receiver on a receiving side isdecreased and a bandwidth of the receiver is narrowed, therebydecreasing an optical link loss and increasing an optical power budget.

Embodiment 7

FIG. 14 is a schematic structural diagram of another deframing apparatus1400 in a PON according to an embodiment of the present disclosure. Theapparatus 1400 may be applied in a GPON or an XG-PON. When the apparatus1400 is applied in a GPON system, the apparatus 1400 is a MAC module ofan ONU at 2.488 Gbps. When the apparatus 1400 is applied in an XG-PONsystem, the apparatus 1400 is a MAC module of an ONU at 10 Gbps. Asshown in FIG. 14, the apparatus 1400 includes a receiving module 1410configured to receive a downstream data stream, where the downstreamdata stream includes a first TC frame and a second TC frame, where adownstream rate of the first TC frame is 2.488 Gbps or 10 Gbps, adownstream rate of the second TC frame is 1/N of the downstream rate ofthe first TC frame, and a sum of frame lengths of the first TC frame andthe second TC frame is 125 μs, where N is an integer greater than 1, anobtaining module 1420 configured to obtain the second TC frame, arestoration module 1430 configured to perform bit mapping restoration onthe second TC frame to generate a third TC frame, where the bit mappingrestoration refers to restoration of every N bits in the second TC frameto one bit, and a parsing module 1440 configured to parse the third TCframe.

Optionally, the apparatus 1400 further includes a descrambling module(not shown), where the descrambling module is configured to performdescrambling on the second TC frame.

Optionally, the apparatus 1400 further includes a decoding module (notshown), where the decoding module is further configured to performdecoding on the second TC frame.

In this embodiment of the present disclosure, further, an opticalreceiver of the ONU receives a downstream data stream, the downstreamdata stream is transmitted to a MAC module of the ONU for processing,and after the receiving module 1410 receives the downstream data stream,when the receiving module 1410 identifies a Psync field in a PCBd fieldof the second TC frame, the receiving module 1410 performssynchronization with the second TC frame according to the Psync field inthe PCBd field.

Further, the obtaining module 1420 is further configured to discard apseudo GEM frame, FEC parity data, and the first TC frame according toframe length information of the second TC frame that is identified by anAlen field in PCBd of the second TC frame to obtain the second TC frame.

A person of ordinary skill in the art should understand that bit mappingis performed on the second TC frame on a sending side, and the second TCframe needs to be restored on a receiving side, that is, the bit mappingand the bit mapping restoration are mutually inverse operations.

It should be noted that specific actions performed by modules inEmbodiment 7 are steps in the method in Embodiment 4 above, and thespecific actions and the steps have a same effect. Details are notdescribed herein again.

FIG. 15 is a schematic structural diagram of a deframing apparatus 1500according to an embodiment of the present disclosure. Referring to FIG.15, the apparatus 1500 includes a processor 1510, a memory 1520, acommunications bus 1530, and a communications interface 1540. Theprocessor 1510, the memory 1520, and the communications interface 1540are connected to and communicate with each other using thecommunications bus 1530. The processor 1510 may be a single-core ormulti-core CPU, an ASIC, or is configured as one or more integratedcircuits implementing this embodiment of the present disclosure. Thememory 1520 may be a high-speed RAM, or may be a non-volatile memory,for example, a flash memory, or at least one magnetic disk storage. Thememory 1520 is configured to store a computer executable instruction.Further, the computer executable instruction may include program code.

The processor 1510 runs the computer executable instruction, andfurther, the processor 1510 is configured to perform the method stepsdescribed in the method in Embodiment 3.

Further, in terms of physical entities, for the deframing apparatus, anFPGA, an ASIC, an SoC, a CPU, an NP, a DSP, an MCU, a PLC, or anotherintegrated chip may be used.

In this embodiment of the present disclosure, the deframing apparatus1500 is provided on a receiving side. In a downstream data streamreceived by the apparatus 1500, a line rate corresponding to a second TCframe is lower than a line rate of a first TC frame such that comparedwith a downstream rate in the other approaches, in this embodiment ofthe present disclosure, a rate of a receiver on a receiving side isdecreased and a bandwidth of the receiver is narrowed, therebydecreasing an optical link loss and increasing an optical power budget.

Embodiment 8

This embodiment of the present disclosure provides a PON system. The PONsystem includes an OLT, a first ONU, and a second ONU. The OLT isconnected to the first ONU and the second ONU using an ODN. As shown inFIG. 2 or FIG. 3, the OLT configured to generate a first TC frame and asecond TC frame separately, where a downstream rate of the first TCframe is 2.488 Gbps or 10 Gbps, a downstream rate of the second TC frameis 1/N of the downstream rate of the first TC frame, and a sum of framelengths of the first TC frame and the second TC frame is 125 μs, where Nis an integer greater than 1, perform bit mapping on the second TC frameto generate a third TC frame, where the bit mapping refers toidentifying each bit of the second TC frame using N bits, and send thefirst TC frame and the third TC frame to the first ONU and the secondONU, the first ONU configured to receive the first TC frame and thethird TC frame, and perform synchronization with the first TC frame, andparse the first TC frame, and the second ONU configured to receive thefirst TC frame and the third TC frame, and obtain the third TC frame,and perform bit mapping restoration on the third TC frame to generatethe second TC frame, and parse the second TC frame.

It should be understand that Embodiment 8 of the present disclosure is asystem embodiment of Embodiments 1 to Embodiment 7, and certainly, thedescriptions of Embodiments 1 to Embodiment 7 are also applicable tothis embodiment of the present disclosure, and for description abouttechnical details, refer to the descriptions of Embodiments 1 toEmbodiment 7, and details are not described herein again.

In addition, the terms “system” and “network” may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases: only Aexists, both A and B exist, and only B exists. In addition, thecharacter “/” in this specification generally indicates an “or”relationship between the associated objects.

It should be understood that in the embodiments of the presentdisclosure, “B corresponding to A” indicates that B is associated withA, and B may be determined according to A. However, it should further beunderstood that determining A according to B does not mean that B isdetermined according to A only, that is, B may also be determinedaccording to A and/or other information.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware, computer software, or a combination thereof. Toclearly describe the interchangeability between the hardware and thesoftware, the foregoing has generally described compositions and stepsof each example according to functions. Whether the functions areperformed by hardware or software depends on specific applications anddesign constraint conditions of the technical solutions. A personskilled in the art may use different methods to implement the describedfunctions for each specific application, but it should not be consideredthat the implementation goes beyond the scope of the present disclosure.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing method embodiments, anddetails are not described herein again.

In the several embodiments provided in the present application, itshould be understood that the disclosed system, apparatus, and methodmay be implemented in other manners. For example, the describedapparatus embodiment is merely an example. For example, the unitdivision is merely logical function division and may be other divisionin actual implementation. For example, a plurality of units orcomponents may be combined or integrated into another system, or somefeatures may be ignored or not performed. In addition, the displayed ordiscussed mutual couplings or direct couplings or communicationconnections may be implemented through some interfaces. The indirectcouplings or communication connections between the apparatuses or unitsmay be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. A part or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments of the present disclosure.

In addition, functional units in the embodiments of the presentdisclosure may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units are integratedinto one unit. The integrated unit may be implemented in a form ofhardware, or may be implemented in a form of a software functional unit.

When the integrated unit is implemented in the form of a softwarefunctional unit and sold or used as an independent product, theintegrated unit may be stored in a computer-readable storage medium.Based on such an understanding, the technical solutions of the presentdisclosure essentially, or the part contributing to the otherapproaches, or all or a part of the technical solutions may beimplemented in the form of a software product. The software product isstored in a storage medium and includes several instructions forinstructing a computer device (which may be a personal computer, aserver, or a network device) to perform all or a part of the steps ofthe methods described in the embodiments of the present disclosure. Theforegoing storage medium includes any medium that can store programcode, such as a universal serial bus (USB) flash drive, a removable harddisk, a ROM, a RAM, a magnetic disk, or an optical disc.

The foregoing descriptions are merely specific implementation manners ofthe present disclosure, but are not intended to limit the protectionscope of the present disclosure. Any modification or replacement readilyfigured out by a person skilled in the art within the technical scopedisclosed in the present disclosure shall fall within the protectionscope of the present disclosure. Therefore, the protection scope of thepresent disclosure shall be subject to the protection scope of theclaims.

1. A framing method in a passive optical network (PON), comprising:separately generating a first transmission convergence (TC) frame and asecond TC frame, wherein a downstream rate of the first TC framecomprises 2,4888 gigabits per second (Gbps) or 10 Gbps, wherein adownstream rate of the second TC frame comprises 1/N of the downstreamrate of the first TC frame, wherein a sum of frame lengths of the firstTC frame and the second TC frame comprises 25 microseconds (μs), andwherein N is an integer greater than 1; performing bit mapping on thesecond TC frame to generate a third TC frame, wherein the bit mappingrefers to identifying each bit of the second TC frame using N bits; andsending the first TC frame and the third TC frame to an optical networkunit (ONU).
 2. The method according to claim 1, further comprisingperforming first coding on the second TC frame, wherein the first codingcomprises one of Reed-Solomon code (RS) (255,239) coding, RS (248,216)coding, low-density parity-check code (LDPC) coding, or cascade forwarderror correction (FEC) coding.
 3. The method according to claim 1,comprising scrambling the second TC frame.
 4. The method according toclaim 1, further comprising inserting a pseudo gigabit-capable PONencapsulation method (GEM) frame header into the third TC frame.
 5. Themethod according to claim 4, wherein inserting the pseudo GEM frameheader into the third TC frame comprises: inserting a placeholder intothe third TC frame; scrambling the third TC frame into which theplaceholder is inserted; and filling the placeholder the pseudo GEMframe header.
 6. The method according to claim 5, further comprisingperforming second coding on the first TC frame and the third TC frameinto which the pseudo GEM frame header is inserted, wherein the secondcoding comprises one of Reed-Solomon code (RS) (255,239) coding, RS(248,216) coding, low-density purity-check code (LDPC) coding, orcascade forward error correction (FEC) coding.
 7. The method accordingto claim 6, further comprising scrambling the first TC frame and thethird TC frame after the second coding.
 8. The method according to claim1, wherein a physical control block downstream (PCBd) field of thesecond TC frame comprises a field indicating a frame length of thesecond TC frame.
 9. The method according to claim 1, wherein a framelength of the first TC frame comprises an integer multiple of 239 bytes.10. The method according to claim 1, wherein a frame length of the firstTC frame comprises an integer multiple of 248 bytes.
 11. A deframingmethod in a passive optical network (PON), comprising: receiving adownstream data stream comprising a first transmission convergence (TC)frame and a second TC frame, wherein a downstream rate of the first TCframe comprises 2.488 giga bits per second (Gbps) or 10 Gbps, wherein adownstream rate of the second TC frame comprises 1/N of the downstreamrate of the first TC frame, wherein a sum of frame lengths of the firstTC frame and the second TC frame comprises 125 microseconds (μs), andwherein N is an integer greater than 1; obtaining the second TC frame;performing bit mapping restoration on the second TC frame to generate athird TC frame, wherein the bit mapping restoration refers torestoration of every N bits in the second TC frame to one bit; andparsing the third TC frame.
 12. The method according to claim 11,further comprising descrambling the second TC frame.
 13. The methodaccording to claim 11, further comprising decoding the second TC frame.14. The method according to claim 11, wherein obtaining the second TCframe comprising removing, according to frame length information of thesecond TC frame from a physical control block downstream (PCBd) field ofthe second TC frame, a pseudo gigabit-capable PON encapsulation method(GEM) frame from, the received second TC frame to obtain the second TCframe.
 15. A framing apparatus, comprising: a memory comprisinginstructions; and a processor coupled to the memory, wherein theinstructions cause the processor to be configured to: generate a firstgigabit-capable passive optical network (GPON) transmission convergence(TC) frame and a second TC frame separately, wherein a downstream rateof the first TC frame comprises 2,488 gigabits per second (Gbps) or 10Gbps, wherein a downstream rate of the second TC frame comprises 1/N ofthe downstream rate of the first TC frame, wherein a sum of framelengths of the first TC frame and the second TC frame comprises 125microseconds (μs), and wherein N is an integer greater than 1; performbit mapping on the second TC frame to generate a third TC frame, whereinthe bit mapping refers to identifying each bit of the second TC frameusing N bits; and send the first TC frame and the third TC frame to anoptical network unit (ONU).
 16. The apparatus according to claim 15,wherein the instructions further cause the processor to be configured toperform first coding on the second TC frame, wherein the first codingcomprises one of Reed-Solomon code (RS) (255,239) coding, RS (248,216)coding, low-density parity-check code (LDPC) coding, or cascade forwarderror correction (FEC) coding.
 17. The apparatus according to claim 15,wherein the instructions further cause the processor to be configured toscramble the second TC frame.
 18. The apparatus according to claim 15,wherein instructions further cause the processor to be configured toinsert a pseudo GPON encapsulation method (GEM) frame header into thethird TC frame.
 19. The apparatus according to claim 18, wherein theinstructions further cause the processor to be configured to: insert aplaceholder into the third TC frame; scramble the third TC frame intowhich the placeholder is inserted; and fill the placeholder using thepseudo GEM frame header.
 20. The apparatus according to claim 19,wherein the instructions further cause the processor to be configured toperform second coding on the first TC frame and the third TC frame intowinch the pseudo GEM frame header is inserted, wherein the second codingcomprises one of Reed-Solomon code (RS) (255,239) coding, RS (248,216)coding, low-density parity-check code (LDPC) coding, or cascade forwarderror correction (FEC) coding.
 21. The apparatus according to claim 20,wherein the instructions further cause the processor to be configured toscramble, the first TC frame and the third TC frame after the secondcoding.
 22. The apparatus according to claim 15, wherein a physicalcontrol block downstream (PCBd) field of the second TC frame comprises afield indicating a frame length of the second TC frame.
 23. A deframingapparatus, comprising: a memory comprising instructions; and a processorcoupled to the memory, wherein the instructions cause the processor tobe configured to: receive a downstream data stream comprising a firsttransmission convergence (TC) frame and a second TC frame, wherein adownstream rate of the first TC frame comprises 2.488 gigabits persecond (Gbps) or 10 Gbps, wherein a downstream rate of the second TCframe comprises 1/N of the downstream rate of the first TC frame,wherein a sum of frame lengths of the first TC frame and the second TCframe comprises 125 microseconds (μs), and wherein N is an integergreater than 1; and obtain the second TC frame; perform bit mappingrestoration on the second TC frame to generate a third TC frame, whereinthe bit mapping restoration refers to restoration of every N bits in thesecond TC frame to one bit; and parse the third TC frame.
 24. Theapparatus according to claim 23, wherein the instructions further causethe processor to be configured to descramble the second TC frame. 25.The apparatus according to claim 23, wherein the instructions furthercause the processor to be configured to decode the second TC frame. 26.The apparatus according to claim 23, wherein the instructions furthercause the processor to be configured to discard, according to framelength information of the second TC frame from a field in a physicalcontrol block downstream (PCBd) of the second TC frame, a pseudogigabit-capable passive optical network encapsulation method (GEM) frameto obtain the second TC frame.